The present invention relates to an improvement in a method of preventing drill mud loss in boring a hole in the ground. More particularly, the mentioned method is applicable to boring of a hole in the ground with drilling mud introduced into the hole for purposes of hole wall stabilization, slime removal and so forth. When the drilling mud is getting lost to the soil, a chemical liquid comprising an isocyanate compound or including an isocyanate compound as a main component is introduced into a depth of the hole to seal a position of drilling mud leakage with a cured product of the chemical liquid.
The above chemical liquid has excellent functional features from the point of view of utility and reliability. To be more particular, this chemical liquid which is insoluble to water and reactive to added water positively gelates without getting diluted or otherwise affected by the presence of underground water streams. Introduction of the chemical liquid to the leaking position is carried out easily and reliably and reliably stopping treatment is effected in a short time even in cases of deep boring since curing reaction of the chemical liquid within injection piping is checked and the chemical liquid is caused to gelate rapidly at the leaking position. Furthermore, not only is the leaking position treated but also hole walls adjacent thereto are reinforced whereby the sealed part is strong against impacts of subsequent boring. Cured product of the chemical liquid formed in the bore hole is a mass of low strength containing numerous bubbles therein, and therefore presents no problem to the subsequent boring operation.
In known methods, however, the described chemical liquid is merely introduced to the depth of the hole, and therefore a wasteful amount of the liquid is required particularly where large cracks are present as in deep rock formations. Since this kind of chemical liquid is very expensive, the prior art methods have a great disadvantage in terms of economy, and also other disadvantages such as of taking long time in some cases to provide treatment to the drilled mud leakage.